Urriak Uruk
Gaming is fun, and fun is for everyone
I think such a product isultimately likely, but I wouldn't bet on it that soon: Dark Sun and Planescape will come first, probably Dragonlance, and possibly Spelljammer.
I predict a 2024 Greyhawk anniversary release.
But, I think Ghosts of Saltmarsh might be something that we see repeated: D series, A Series, N1 probably (the single best selling older edition product on the DMsGuild, randomly, and just around the corner from Saltmarsh), and those sorts of things set in new Greyhawk sandboxes here and there.
Reason i think it could be coming a lot sooner is that it doesn't need a bunch of new rules that need to first be tested through Unearthed Arcana. Much easier to push out quickly.